The first oviraptor was discovered in Mongolia in 1922. It was given its name, which means “egg thief”, because it was found near a nest of what appeared to be Protoceratops eggs.

In 1993, however, Mark Norell of the American Museum of Natural History found a fossilised embryo in an identical egg. He recognised it as a kind of oviraptor, suggesting the original thief was in fact a parent.

The next year, Norell was back in Mongolia when he spotted bones and claws protruding from the sand. But Norell had limited space in his trucks. The bulky fossil might have stayed where it was had team member Luis Chiappe not injured his foot. He wanted to collect a specimen rather than walk around searching for more. A day or two later, Chiappe drove up to Norell and another team member, Jim Clark. “We found something you won’t believe,” Chiappe told them.

The skull of the dinosaur was missing. But much of the rest of the skeleton was present – and under it there was a nest of eggs. “It’s clear it was sitting on the nest,” says Clark, now at George Washington University in Washington DC. What’s more, it was sitting in exactly the same position birds adopt when incubating their eggs. There had been hints before that some dinosaurs brooded their eggs, but ...

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